Trying to understand the precession of the equinoxes - please help

[Quetzalcoatl]

Hello Everybody,

My name is Michiel Luyken :wave: and I am from Holland, currently living and working in the UK in Portsmouth as Expatriate and working in the dredging industry. I have always been interested in our solar system. Recently I have been reading a book about ancient civilisations and in particular their efforts to establish the Seasonal Equinoxes and Solstices.

I have been trying to understand the so called precession of the equinoxes and in particular the shifting of the zodiac belt against the rising point of the sun. Due to the presession of the Earth the Zodiac belt shifts 1 degree every 72 years or 360 degrees in 25,920 years. But I just don't understand it. I reason as follows and please correct me because I know I am wrong:

The Sun is static (or at least lets asume it is static)

The Zodiac belt with 12 constellations is static (one every 30 deg).

The Earth revolves around the Sun and precesses 360 deg in 25,920 years under an angle of approx 23.5 deg

Lets assume the Earth is located at the Vernal equinox

When the Sun rises it will rise today within the constellation Pisces

When we look 12,960 years from now, the angle of precession will be the inverse of today.

Lets assume again the Earth is at the Vernal equinox.

When the Sun rises it will rise, according to what I read in a constellation opposite Pisces.

But how is this possible, because the zodiac has not moved and the sun is in the same position, so if the sun rises, how is it possible that you will see the constallation opposite Pisces? The angle under which you will see the constellation must be different because the Earth's angle is opposite of that 12,960 years ago. But I just cannot get my head around the fact :scratch: that the complete zodiac belt appears to shift 360 deg in 25,920 years.

For the person who can explain this to me, I really appreciate :cheers: ,

Thanks

A newbie

[Brandon]

check out this video. it explains it a bit http://www.youtube.com/watch?v=A_E0vfP79yE& i think between 0:15 to 2:10

[Quetzalcoatl]

Thanks..., but I still don't understand (I am not a brain surgeon and work in the Dredging industry...)

The video shows a very short animation of the earth and zodiac belt. The shown vernal equinox in Pisces is shown behind the earth and then the sun, while in my understanding the Pisces should be behind sun and than the earth...The sun rises in the constellation Pisces so we should see from the earth, first the sun and then the constellations. Maybe I don't understand the precession principle but in my understanding it is a circular motion of an angle decribing a cone. How can that justify a complete shift of the zodiac belt????? Does anyone maybe have a more clear explantion?

[Brandon]

ok this series MIGHT help a little more http://www.youtube.com/watch?v=_g4xU5qnvPY . just because u work in the industry does not mean u are not smart lol. ur just as smart as anyone here. I had a hard time in school grasping the concept, probably because it is so hard to explain and i dont think that i could explain it on here. its one of those things that you visually need to learn

[adamsp123]

The earth is spinning like a top and like a top that is getting slow it has a wobble.

Now this wobble means that the earths equator if expanded out into space cuts the line of the ecliptic in 2 places. One of these places, and was used for navigational calculation, was called the first point of Aries.

Now because of the wobble the First point of Aries moves and in fact I believe it is no longer in the constellation of Aries and hence all the astrological signs are out by one star sign! This movement is the progression of the Equinoxes (because it will change the date of the summer and winter Equinoxes over time) also the wobble means the pole star will in time be nowhere near north.

A) hope I am right - I am sure someone will correct me if I am wrong

you understand my explanation

Pete

[timetraveller]

hello Quetzalcoatl

OK to try and make this easier for you I have drawn this very simple diagram for you to try and explain precession if you look at the image you will see i have drawn the normal Earths tilt in blue and you will notice the position of the viewing line also in blue for both Summer and winter solstices but because the Earth's axis wobbles you will see once precession has occur ed the axis has actually reversed drawn in red and so has the viewing line they are in effect looking at the opposite side of the sky and so consequentially the sun will appear to rise in a different part of the sky from your location hope this is clearer apologise for the drawing I am no artist

Regards Pete

(click to enlarge)

(click to enlarge)

[Quetzalcoatl]

Thanks for your explanations, But I think I found the correct answer to my questions by surfing on the internet, please correct me if I am wrong. The below chart shows the precession of the earth over time (a great year) Because the angle of the axis varies so do also the seasons, so what is spring equinox now is the autumn equinox 12,960 years years from now (180 deg shift) So this means the actual location of the earth compared to the sun is not different over time. But because the seasons change, it also means that the spring equionox 12,960 years from now shows exactly a shift of 180 deg in the zodiac belt. I hope my understanding is correct.

(click to enlarge)

[Kaptain Klevtsov]

If you imagine standing outside the orbit of the Earth looking at the Earth with the sun behind it at the equinox, and the orbit of the Earth goes horizontal from your point of view, then the Earth's axis will not be vertical, but tipped over. Well the tipped over bit gives the seasons as you are already aware.

The precession refers to the way that the tip angle moves round, so the next year you would have to stand at a different point outside the solar system to see the sun behind the earth at the equinox.

Precession is what you see in a gyroscope (kid's toy). The spinning wheel represents the earth in orbit and the movement of the cage represents the motion of the earth's axis over a very long time.

HTH

Kaptain Klevtsov